A variety of mechanical machines, such as drilling, tunnelling and continuous mining machines are available for cutting rock formations. One drawback of these prior art machines is that they are designed primarily for working relatively soft rock formations and as a result, application of these machines and techniques to hard rock such as granite and basalt is either not possible or inefficient due to slow speed and increased tool wear.
In order to address this problem, the prior art reveals thermally treating the hard rock formations prior to cutting in order to introduce subsurface fractures and weaken the rock. These prior art methods and devices reveal the use of a variety of thermal sources such as gas jets, lasers and radiant electric heaters and the like, but have proven less than optimal due to their limited effect, large expense and additional time required.
The prior art also reveals thermally treating rock formations using microwaves in order to introduce thermal expansion causing tensile stress thereby fracturing and weakening the rock so that it is more susceptible to subsequent excavation by mechanical mining machines. One drawback of these prior art methods is that, as the microwaves are not optimised in order to maximise the effect of thermal expansion weakening of the rock is reduced, or alternatively high power microwave sources must be used thereby reducing efficiency.